This invention relates to decorative sheets which provide a change or fade in opacity across the sheet. The decorative sheets are useful in vehicles, such as automobiles, to provide detailing and customization.
Automotive design and manufacture present a unique set of problems in the selection of materials and processes used in the manufacture of automobile bodies. As a form of transportation, automobiles are unique because most buyers want a vehicle to have a certain individual styling. A recent trend in the automobile industry is toward production of distinctive vehicles styled to attract specific groups of consumers. This change has required the car builder to shift production from a few models manufactured in large volumes to a larger number of more distinctive body styles. These developments have demanded from the manufacturer both styling flexibility and reasonable tooling costs for each body style.
It is difficult to provide a conventional process for painting an automobile which provides a gradual and consistent fade of one color into another. Careful process controls are required to provide a fade of one color into another. Even if it was able to provide such paint, it would require a multistep process and be labor intensive. The expense would make the production unfeasible. It is desirable to have a film which provides a fade across its surface from one color to another. The sheet could be applied to the vehicle surface where the color of the sheet blends to a clear overlay, thus producing the desired fade effect.
A number of technical problems must be overcome in order to use such a film for exterior automotive applications. For instance, the film must be defect-free before being applied. The film also must initially be repositionable. Therefore, the adhesive should have a relatively low initial tack value which increases over time and therefore becomes increasingly more difficult to remove. The film must avoid long-term delamination at the adhesive interface between the film and the car body panel; and inter-layer delamination between the various coatings in the finished composite film also must be avoided.
Durability properties are also critical in producing a paint coat capable of exterior automotive use. The paint coat must avoid exhibiting defects when exposed to mechanical impact and avoid deterioration of the surface from exposure to chemicals and to the weather. Among other properties, the film requires good cleanability, UV and heat resistance.
A paint system that produces the toughness or hardness necessary for exterior automotive use also must have the elongation properties necessary for applying the film around complex three-dimensional shapes without cracking, or producing stress lines or other surface non-uniformities. Certain paint films having good elongation at elevated temperatures are not necessarily applicable to the present invention which requires good elongation at room temperatures.
Thus, the desired paint system should have a critical combination of many physical properties in order to produce a surface capable of exterior automotive use, while retaining the desired surface characteristics after the application process. However, some physical properties tend to be mutually incompatible in such a process. For instance, a paint system may have good durability properties such as hardness, toughness, weatherability and the like; but the same paint system may not have sufficient room temperature elongation to be applied smoothly over a complex shape by a pressure-sensitive adhesive. Some paint systems have sufficient elongation to permit application over a complex shape, but they are too soft and therefore lacking in the necessary hardness and/or durability properties.
U.S. Pat. No. 5,518,786 relates to an exterior automotive laminate with pressure-sensitive adhesive. The patent relates to a flexible decorative sheet for use in surfacing an automotive body panel which includes a first polyester carrier sheet having a high gloss surface, a clear coat of a weatherable optically clear polymer containing fluorocarbon resin and acrylic resin coated on the surface of the first carrier sheet, a tie coat on the clear coat, and a color coat containing a chlorinated polymer with dispersed pigments cast on the tie coat and dried. A pressure-sensitive adhesive is formed on a second polyester carrier sheet and then laminated to the exposed face of the color coat to form a pressure-sensitive adhesive-backed composite paint coat between the outer carrier sheets which form protective removable backing sheets for the resulting laminate.
It is desirable to have a decorative sheet which provides the ability to fade from one color to another, i.e., having an opacity change over surface which is durable and has the acceptable appearance properties for exterior automotive use.
The present invention relates to multilayer decorative sheet comprising: (a) an. outer heat resistant carrier first carrier sheet, (b) a clear coat, which in one embodiment, comprises a blend of a fluorocarbon polymer and an acrylic or methacrylic resin, coated on the carrier sheet, (c) a tie coat layer on the clear coat layer, (d) fade print coat on the tie coat layer, (e) an optional back coat on the print layer, (e) a pressure-sensitive adhesive, and (f) a second carrier sheet adhered to the pressure-sensitive adhesive. When used on a vehicle the graphic has an opaque portion, such as a metallic finish, at the topside of the vehicle and the opacity fades over the graphic to clear, thereby revealing the vehicle""s color under the decorative sheet. The fading occurs across the width of the graphic. In one embodiment, the fade is gradual and reveals little stark changes in opacity. The present invention provides a decorative laminate which provides a fade from one opacity to another wherein the sheet has a combination of good durability, elongation, opacity, gloss and DOI levels and a defect-free surface.